Polyurethane-ureas containing urealinked piperazine compounds



United States Patent 3,281,397 PfiLYlURlETHANE-UREAS CONTAINING UREA- LINKED PHPERAZINE COMPOUNDS Seymour L. Axelrod, Trenton, Mich., assignor to Wyandotte Chemicals Corporation, Wyandotte, Mich., a corporation of Michigan No Drawing. Original application Jan. 26, 1959, Ser. No. 788,795. Divided and this application Feb. 10, 1964, Ser. No. 343,464

1 Claim. (Cl. 26077.5)

The present invention relates to new and useful polyurethane-urea polymers and is more particularly concerned with polyurethane-urea polymers containing heterocyclic-urea-linked chain structure. More specifically, the present invention relates to polyurethaneurea polymers incorporating urea-linked piperazine compounds, which are prepared by the chain-extension of isocyanate-terminated polyurethanes, and to a method of producing said urea-linked piperazine-modified polyurethanes.

This is a division of copending application Serial No. 788,795, filed January 26, 1959, now abandoned.

The chemistry and technology of polyurethanes has made great strides since the early work of Otto Bayer reported in Angewandte Chemie A 59, 257 (Sept. 1947). Much of this later work has been summarized in the report of A. C. Beutel et a1. entitled Polyurethanes, published in 1956 by Polyurethane Associates, Cambridge, Massachusetts; in the B. A. Dombrow monograph entitled Polyurethanes published in 1957 by Reinhold Publishing Corporation, New York; and in the Kirk- Othmer Encyclopedia of Chemical Technology, First Supplement Volume, under the heading Urethane Polymers. Numerous patents issued in recent years also give evidence of tremendous activity in this art.

Among the noteworthy advances in this area may be mentioned the production of polyurethane-urea polymers of elastomeric or plastic nature by the chain-extension of isocyanate-terminated polyurethane polymers by reaction With water, thereby converting isocyanate groups to amine groups which then react with other isocyanate groups to form urea linkages. Diamines have also been reacted directly with isocyanate-terminated polyurethanes for purposes of chain extension through formation of urea linkages. The diamines produced by hydrolysis of isocyanates and likewise added as such to isocyanate-terminated polyurethanes have notably been primary diamines, such as tolylene diamine, an arylene diamine, and the like. Alkylene and cycloalkylene diamines have also been proposed as chain extenders of polyurethane polymers for purposes of producing elastomeric or plastic products.

These prior art polyurethane-urea polymers produced by chain extension using primary diamines are generally characterized by difiiculty of processing on conventional rubber equipment, difliculty of processing to obtain useful values of tensile strength through vulcanization unless unsaturation has been built into the molecule, and are frequently highly colored. At utilizable tensile strength values, such products have been extremely difiicult to process, due to the accompanying high degree of hardness. One factor to which such hardness can be attributed is the presence of two hydrogen atoms on each of the two diamine nitrogens which, upon reaction with an isocyanate-terminated polyurethane, produces a urea linkage in which each nitrogen atom bears a hydrogen atom which, being active, is replaceable by an isocyanate radical in the classic biuret formation reaction to form a urea linkage which is quadruplicately crossed-linked, thus:

wherein R is the primary diamine residue and R is the isocyanate-terminated polyurethane residue, and wherein R", R', R"", and R"' are the residues of isocyanates or isocyanate-terminated polymer chains. Another and more likely explanation for difliculty in processing of such polymers prepared from primary diamines is the formation of hydrogen bonds due to the extra active hydrogen atoms on the urea nitrogens.

While a multi-dimensional lattice structure is in theory highly desirable and even necessary for elastomeric qualities, an excess of active hydrogens and corresponding increased orosslinking or hydrogen-bonding is without queswhere the N atoms are a part of the piperazine ring and RA represents the alcohol residue. These polyurethanes, as will be noted, have no possible cross-linking centers for establishment of tri-dimensional lattice-type molecules and, in fact, are even devoid of active hydrogen atoms attached to the N atom of the urethane linkage, and thus would be completely incapable of setting up cross linkages or branches, even through allophanate production or hydrogen-bonding, if such concepts were suggested. Of course, isocyanates were not present in the reaction productive of such prior art piperazine-containing polyurethanes, an entirely different process approach having been employed. In addition, no urea link-ages are present in these molecules, so that biuret cross-linking or branching would be likewise impossible. These piperazine polyurethanes are, therefore, entirely unsuited for use as elastomers and were never intended as such.

So far as I am aware, piperazines have never been employed or suggested as chain extenders for polyurethane polymers, nor has it been suggested to incorporate urealinked piperazines int-o such polyurethane-urea molecules, or that any advantage would be realized from so doing.

It has now been found that piperazine compounds containing only those two active hydrogen atoms attached to the two nitrogen atoms of the piperazine ring and being otherwise devoid of reactive groups, for example, piperazine compounds of the formula:

oHofi R R wherein R is selected from hydrogen and lower-alkyl, especially methyl, may be incorporated in polyurethaneurea polymers by the reaction thereof with isocyanateterminated polyurethane polymers to give new and valuable polyurethane-urea polymers characterized by urealinked heterocyclic intermediate and terminal chain structure.

Representative piperazine compounds which may be employed are, for example, piperazine itself, but preferably the C-substituted lower-alkyl piperazines, such as 2- methylpiperazine, 2-ethylpiperazine, Z-butylpiperazine, 2- the mixture of isomers and the individual cis and trans hexylpiperazine, 2,5-dimethylpiperazine, 2,6-dimethylisomers), attain useful tensile strength values within a piperazine, 2,3dimethylpiperazine, and 2,3,5,6-tetramethready processability range and therefore need not undergo ylpiperazine. Of the piperazines which exist in stereovulcanization to attain utilizability. The product of Exisomeric forms, such as 2,5-dimethylpiperazine, the cis 5 ample 4, for instance, exhibits very outstanding propform is preferred for processability and the trans form erties for an unvulcanized elastomer and the product as lending superior tensile characteristics to the polyureof Example 3 is representative of a utilizable plastic in thane-urea polymers incorporating same. In addition, accord with the present invention.

compounds wherein a plurality of methyl or other alkyl The piperazine-containing polyurethane-ureas, moregroups are attached to a single carbon atom, such as 2,2- over, exhibit superior characteristics when compared with dimethylpiperazine or 2,2,5,5-tetramethylpiperazine, may polyol, e.g., butanediol, cross-linked polyurethanes. Since b l d, this use of polyols is a common practice for the chain In contrast to the foregoing representations of the extension and cross-linking of polyurethanes, the supemore or less successful attempts of the prior art to obriority in regard to both polyether and polyester-based tain a solution to some of the aforementioned problems, polyurethanes is obviously of interest from more than a the recurring piperazine-containing urea linkages formed mere technical standpoint. in accord with the present invention are of the general It is accordingly an object of the present invention to formula; provide new and useful polyurethane-urea polymers inm corporating urea-linked piperazine compounds and a RNH-C ON N-CO-NH- method of producing same. It is a further object of the U invention to provide new and useful elastomeric to plastic wherein the urea-linked piperazine-modified polwrethane-ureas. Still f a further object of the invention is to provide such novel U urea-linked piperazine-modified polyurethane-ureas having in general a lighter color and an improved ratio of indicates the nitrogen atoms of the piperazine ring, said tensile strength to hardness. An additional object is the ring being devoid of reactive groups. These linkages, it provision of such urea-linked piperazine-modified polywill be noted, contain in each case two active centers for urethane-ureas which are comparatively softer and therecross linking, the two active urea hydrogen atoms for fore more readily processa-ble at higher values of tensile biuret formation or hydrogen-bonding. strength. Still a further object is the provision of such- These piperazine-containing urea linkages, to attain (16- type polyurethane-ureas which are processable and utisirable properties, should occur at least once for every lizable per se as elastomers at tensile strength values in 8000 molecular weight units of the polyurethane-urea excess of 2000 p.s.i. and at corresponding Shore A hardproduct. There may be considerably more than one ness values not substantially exceeding a value of sixty. of these linkages for every 8000 molecular Weight units Other objects of the invention will become apparent hereof the polyurethane-urea polymer but, on the average, it inafter. is preferred to have not more than one of these linkages In brief, the urea-linked piperazine-containing polyfor every 700 molecular weight units of product. urethane-urea polymers of the present invention are pre- In its simplest form, such exemplary polyurethane-urea pared by reacting the selected piperazine compound (II) polymer molecule radicals may be represented as follows: with the selected isocyanate-terminated polyurethane R R CH-CH l -N NC ONHYNHO OOXOC O-NH--YNH-C 0 OHCH J wherein n is an integer, preferably a large whole number, polymer (I) according to either solvent, bulk, or emulsion wherein OXO- is the radical obtained by removtechnique, as more fully set forth hereinafter. The polying the terminal hydrogen atoms of a polymeric glycol and urethane prepolymer (I) is preparable from a large num- Y is the organic radical of the polyisocyanate employed 'ber of polymeric glycols (a) and polyisocyanates (b), in producing the polyurethane. It will be noted that only also as more fully set forth hereinafter. The emulsion four active hy-drogens exist in this radical, two urea hytechnique of chain extension is preferred from the point drogens for biuret formation and two urethane hydrogens of more uniform homogeneity of reaction product.

for allophanate formation, compared to six in the usual polyurethane-urea recurring molecular unit.

These urea-linked piperazine modified polyurethanes T i CYaHate-terminated polyurethane prepolymers Polyurethane prepolymer-Starting materials of the present invention have been found to exhibit supemployed as starting materials according to the presrior properties, especially in the elastomer area, together 61111 invention y be ny Such ype C mp und having a with a desirable light-color. For example, they have an molecular weight in excess of about 500 which may be improved ratio of tensile strength to hardness, which enobtained by the reaction of a selected polymeric glycol ables them to be more readily processed in a compara- (21), having an average molecular weight of at least 250, tively softer state and at higher tensile strength values. With a stoichiometric excess of an organic polyisocyanate Moreover, due to this improved ratio of tensile strength (b). Such prepolymers are capable of amolecular weight to hardness, many of the new polyurethane-ureas may be increase through chain-extension with the particular chainutilized per se as elastomers without further processing inextension agents of the present invention.

asmuch as they exhibit tensile strength values in excess of The polyurethane polymers which may be extended 2000 psi. Since these tensile strength values are ataccording to this invention include those which are pretained at corresponding Shore A hardness values of sixty pared from polyalkylene ether glycols and diisocyanates. or below, they are processable within a useful tensile The term polyalkylene ether glycol as used herein refers strength range. In contrast, comparisons with primary to a polyalkylene ether which contains terminal hydroxy diamine extended polyether type polyurethanes have groups. These compounds are derived from the polymshown that these do not attain useful values of tensile erization of cyclic ethers such as alkylene oxides or distrength within the range of processabiliy, viz., at a hardoxolane or from the condensation of glycols. They are ness value below Shore A 60. Many of the elastomers sometimes known as polyoxyalkylene glycols, polyalkylof the present invention, especially those incorporating the ene glycols, or polyalkylene oxide glycols, or dihydric Z-methylpiperazines and the 2,5-dimethylpiperazines (both polyoxyalkylenes. Those useful in preparing the prodnets of this invention may be represented by the formula HO(RO),,H, in which R stands for an alkylene radical and n is an integer sufiiciently large that the molecular weight of the compound is at least 250, i.e., large enough that the polyoxyalkylene group --(RO),, has a formula weight of at least 232. Not all of the alkylene radicals present need to be the same. Glycols containing a mixture of radicals, as in the compound wherein n and m are together sufiicient for attainment of the desired molecular weight, can be used.

These glycols are either viscous liquids or waxy solids. To be of value in preparing polymers according to this invention, the molecular weight of the glycol should be at least 250 and may be as high as 10,000. It is preferably between 400 and 4000. Polytetramethylene ether glycols, also known as polybutylene ether glycols, may be employed. Polyethylene ether polypropylene ether glycols, having the above-indicated formula, are among the preferred glycols. Polyethylene ether glycols, poly-1,2- propylene ether glycols, polydecamethylene ether glycols, and poly-l,Z-dimethylethylene ether glycols are representative of other operative compounds.

The preferred polymeric glycols (a) are polyoxyalkylene glycols, e.g., polyoxypropylene or polyoxybutylene glycols, of molecular weights between about 400 and 4000, preferably 400 to 2500 for polyoxypropylene glycols and 750 to 4000 for the polyoxybutylene glycols, as well as the polyoxyethylenepolyoxypropylene glycols of molecular Weight between about 1000 and 5000, preferably 1000 to 2000.

Characteristics of representative preferred polyalkylene or polyalkylene ether glycols, including hydroxyl numbers and molecular weights, are found in Table A.

TABLE A.TYPICAL PROPERTIES OF REPRESENTATIVE PREFERRED POLYALKYLENEETHER GLYCOLS Any of a wide variety of organic polyisocyanates (b) may be employed in the reaction, including aromatic, aliphatic and cycloaliphatic diisocyanates and combinations of these types. Representative compounds include aromatic diisocyanates, such as 2,4-tolylene diisocyanate, mixtures thereof with 2,6-tolylene diisocyanate (usually about 80/20), 4,4-methylene-bis(phenylisocyanate), and m-phenylene diisocyanate. Aliphatic compounds such as ethylene diisocyanate, ethylidene diisocyanate, propylene- 1,2-diisocyanate, butylene-l,3-diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate and decamethylene diisocyanate, and alicyclic compounds, such as 1,2- and 1,4-cyclohexylene diisocyanates and 4,4-rnethylene-bis(cyclohexylisocyanate) are also operable. Arylene diisocyanates, i.e., those in which each of the two isocyanate groups is attached directly to an aromatic ring, react more rapidly with the polymeric glycols than do the alkylene diisocyanates. Compounds such as 2,4- tolylene diisocyanate in which two isocyanate groups differ in reactivity are particularly desirable. The diisocyanates may contain other substituents, although those which are free from reactive groups other than the two isocyanate groups are ordinarily preferred. In the case of the aromatic compounds the isocyanate groups may be attached either to the same or to different rings. Additional polyisocyanates which may be employed, for example, include: p,p-diphenylmethane diisocyanate, 3,3-dimethyl-4,4-biphenylene diisocyanate, 3,3-dimethoxy-4,4- biphenylene diisocyanate, 3,3-diphenyl-4,4'-biphenylene diisocyanate, 4,4'-biphenylene diisocyanate, 4-chloro-l,3- phenylene diisocyanate, 3,3-dichloro-4,4'-biphenylene di isocyanate, and 1,5-naphthalene diisocyanate, and other polyisocyanates in a blocked or semi-inactive form such as the bis-phenylcarbamates of tolylene diisocyanate, p,p'- diphenylmethane diisocyanate, p-phenylene diisocyanate, and 1,5-naphthalene and 1,S-tetrahydronaphthalene diisocyanate.

Instead of the hydrocarbon portion of the polyether glycols used in forming these polyurethane products being entirely alkylene, it can contain arylene or cycloalkylene radicals together with the alkylene radicals as, for example, in the condensation product of a polyalkylene ether glycol with a,a-dibromop-xylene in the presence of alkali. In such products, the cyclic groups inserted in the polyether chain are preferably phenylene, naphthylene or cyclohexylene radicals or these radicals containing :alkyl or alkylene substituents, as in the tolylene, phenylethylene or xylylene radicals. Elastomers made using polyalkylene-arylene or polyalkylene-cycloalkylene ether glycols have improved freeze resistance as compared with the corresponding elastomers containing no cyclic radicals.

Another class of glycols useful in making polyurethanes extensible according to this invention are the polyalkylene ether-polythioether glycols. Such glycols may be represented by the formula HO(QY) H in which Q represents hydrocarbon radicals, at least some of which are alkylene, Y represents chalcogen atoms, some of which are sulfur and the rest oxygen, and n is an integer large enough so that the glycol has a molecular weight of at least 250. These products may be made by condensing together glycols and thioglycols in the presence of a catalyst such as p-toluenesulfonic acid. As will be noted, these compounds resemble the polyalkylene ether glycols except that some of the alkylene radicals are joined by sulfur rather than oxygen. In each case, however, the compounds have terminal hydroxy groups which take part in the reaction with the organic polyisocyanate.

Also included in the polyurethane products which may be extended according to this invention are those made from a high molecular weight, substantially linear polyester and an organic diisocyanate of the type previously described. Products of this sort are described in the aforementioned Bayer article in Angewandte Chemie, and in US. Patents 2,621,166, 2,625,531 and 2,625,532. The polyesters should have molecular weights of at least 750 and are prepared by reacting together glycols such as ethylene glycol, diethylene glycol, triethylene glycol, trimethylene glycol, 1,2-propylene glycol, tetramethylene gycol, 2,3-butylene glycol, pentamethylene glycol, 1,6- hexylene glycol, and decamethylene glycol, and dicarboxylic acids such as malonic, maleic, succinic, adipic, pimelic, sebacic, oxalic, phthalic, terephthalic, hexahydroterephthalic, and para-phenylenediacetic acids, decameth ylene dicarboxylic acid, and the like. Another useful group of compounds for this purpose are polyester amides having terminal hydroxy groups. The preferred polyesters may be represented by the formula in which Z and Z are hydrocarbon radicals derived from the glycol and dicarboxylic acid respectively and n is an integer large enough so that the molecular weight of the compounds as awhole is at least 750 and that the polyester group (ZOOC-Z'-COO),,ZO- has a molecular formula weight of at least 732. Preferably such polyesters have a molecular weight in excess of 1000. The polyester resulting from reaction of adi-pic acid with a mixture of ethylene and propylene glycols is preferred. In the preparation of these polyesters, the glycol is used in at least slight excess so that the polyesters contain terminal hydroxyl groups which are available for reaction with the isocyanates. The same polyisocyanates and reaction conditions useful in preparing polyurethanes from the polyalkylene ether glycols are also useful with the polyesters.

Polyurethane glycols may also be reacted with an organic polyisocyanate to give isocyanate-terminated polyurethanes for use as starting materials in the present invention. The starting polyurethane glycol is prepared by reacting a molar excess of a polymeric glycol, such as a polyalkylene ether glycol, with an organic diisocyanate. The resulting polymer is a polyurethane containing terminal hydroxyl groups which may then be further reacted with additional polyisocyanate to produce the starting isocyanate-terminated polyurethane prepolymer.

Another starting polyurethane prepolymer may be such as disclosed in US. Patent 2,861,981, namely, those prepared from a polyisocyanate and the reaction product of an ester of an organic carboxylic acid with an excess of a saturated aliphatic glycol having only carbon atoms in its chain and a total of eight to fourteen carbon atoms, at least one twocarbon-atom branch per molecule, and having terminal hydroxy groups separated by at least six carbon atoms.

It is obvious, from the above-described methods by which the polyurethane reaction products may be prepared and from the reactants used, that these products will contain a plurality of intralinear radicals of the formula wherein the bivalent radical O-XO-- is obtained by removing the terminal hydrogen atoms of a polymeric glycol, said glycol having a molecular weight of at least 250 and being selected from the group consisting of polyalkyleneether glycols, polyurethane glycols, polyalkylenearyleneether glycols, polyalkylene-cycloalkyleneether glycols, polyalkyleneether-polythioether glycols, polyester amide glycols and polyester glycols of the formula wherein Z and Z' are hydrocarbon radicals and n is an integer, and that a typical isocyanate-terminted polyurethane polymer produced from diisocyanates and dihydric glycols will on an average contain, at a 2/ 1 NCO/ OH ratio, a plurality of intralinear molecules conforming to the formula wherein -O--X-O has the value given previously and Y is the polyisocyanate hydrocarbon radical.

Polyurethane prepolymer-Preparation In the preparation of the starting polyurethane polymer (I), an excess of the organic polyisocyanate (b) over the polymeric glycol (a) is used, which may be only a slight excess over the stoichiometric amount (i.e., one equivalent of polyisocyanate for each equivalent of the polymeric glycol). In the case of a diis-ocyanate and a dihydric polyalkylene ether, the ratio of NCO to OH of the glycol will be at least one to one, and may be up to a 3 to 1 equivalent ratio. The glycol and the isocyanate are ordinarily reacted by heating with agitation at a temperature of 50 to 130 centigrade, preferably 70 to 120 centigrade. nate compound (b) to polymeric glycol (a) is usually and preferably between about 1.321 and 20:1.

The equivalent ratio of organic polyisocya- The reaction is preferably, but not necessarily, effected in the absence of a solvent, when the prepolymer (I) is a fluid at processing temperatures. When it is not, or when it is desired to employ a solvent, convenient solvents are organic solvents having a boiling range above centigrade when the reaction is to be carried out in open equipment. Lower boiling solvents may of course be used where the reaction is carried out in closed equipment to prevent boiling off the solvent at the temperatures of the reaction. Solvents boiling at substantially more than 140 centigrade are difficult to remove from a fiinal chain-extended elastomer :at desirable Working temperatures, although it will be obvious that higher boiling solvents may be employed where the excess solvent is removed by means other than by heating or distillation. The solvent, when used, may be added at the beginning, at an intermediate point, or at the end of the prepolymer stage, or after cooling of the formed prepolymer. The solvents to be used are preferably those in which the reactants have some solubility but in which the final chainextended elastomer is insoluble. Ketones, tertiary alcohols and esters may be used. The aliphatic hydrocarbon solvents such as the heptanes, octanes and nonanes, or mixtures of such hydrocarbons obtained from naturally occurring petroleum sources such as kerosene, or from synthetically prepared hydrocarbons, may sometimes be employed. Cycloaliphatic hydrocarbons such as methylcyclohexane and aromatic hydrocarbons such as toluene may likewise be used. Toluene and isopropylacetate are preferred solvents. The amount of solvent used may be varied widely. From 25 to 400 parts of solvent per parts of glycol have been found to be operable. The excess solvent, where large amounts are employed, may be separated partially or completely from the polymer prior to emulsification in the water solution, if an emulsion technique is to be employed in the chain extension; sometimes the excess solvent is useful and is allowed to remain during the emulsification stage.

The reactants are cooked for a period sufficient to react most, if not all, of the hydroxy groups, whereafter the prepolymer is allowed to stand and the free NCO Chain extensi0nProcedure In the solvent chain-extension process, the chain-extending agent is added to the isocyanate-termin-ated polyurethane prepolymer reaction medium and mixing continued, with or without further application of heat. During this period the molecular weight of the polyurethane reaction product increases and the mass forms a gel or, in some cases, rubbery chunks. It is then removed from the mixer and molded into sheets, for example, it may be sheeted out on a rubber mill. In some cases, a solution can be formed which may be cast into a film or used for coatings or adhesives.

In producing elastomeric polyurethane-urea latices of the present invention by the emulsion chain extension technique, the equivalent ratio of the organic polyisocyanate (b) and the polymeric glycol (a) is in most cases preferably maintained at from about 1.311 to 2.0: 1: When using these equivalent ratios an initial polyurethane reaction product (I) is obtained which is usually a liquid under processing conditions, which, as illustrated by the examples hereinafter given, can be emulsified directly in an aqueous bath or can first be diluted with inert organic solvents, such as previously mentioned, and then emulsified in an aqueous bath. Where polyalkylene et-her glycols are used in this process, molar ratios of organic diisocyanate to polyalkylene ether glycol higher than about 3 :1 usually yield final polyurethane-urea polymers or mixtures of polymers which are more plastic than elastomeric. Similarly, polyalkylene ether glycols of lower molecular weight, or use of polyisocyanates having more than two NCO groups, also tend to yield polyurethane-urea polymers of a more plastic character.

The amount of piperazine compound (II) used in the chain extension step is such that from 0.5 to 1.5 equivalents of (II) are present in the chain extension reaction for each equivalent of the isocyanate-terminated polyurethane starting polymer) (I), preferably about 1.0 equivalent of (II) for each equivalent of (I). The higher ranges ensure mainly terminal piperazine groups through provision of enough of reactant (II) to react with all of the isocyanate radicals present, although for solvent technique the higher ranges are not ordinarily recommended. For a diisocyanate-dihydric polyalkylene glycol or similar polyurethane, the ratio will usually be one mole of piperazine compound (II) for each mole of isocyanate-terminated polyurethane.

According to the emulsion technique, elastomeric polyurethane-urea latices are produced by reacting the polymeric glycol compound (a) with a stoichiometric excess of an organic diisocyanate (b) and, while the reaction product (I) is in the form of a syrupy liquid, emulsifying it in water or an aqueous solution of the watersoluble or partially water-soluble chain extending agents of the present invention, preferably with vigorous agitation in the presence of an emulsifying agent. Where the initial reaction product (I) is too thick or viscous to emulsify properly in water, it can be diluted with an inert solvent and the resulting solution emulsified in the aqueous bath. If the chain-extending agent is waterinsoluble, it can be added in the form of a solvent solution thereof. The emulsifying agent may be added either to the initial reaction product or to the aqueous medium in which the reaction product is to be emulsified, or may be formed in situ during addition of the reaction product to the said medium.

The piperaziue chain-extending agents of this invention (II), which are water-soluble, may be used in the form of solutions in producing these emulsions or latices since they react more readily with the isocyanate-terminated polyurethane (I) than does water itself. For the same reason, the prepolymer (I) may be emulsified in water just prior to adding the chain-extending agent. The hydrogen on each end of the piperazine molecule reacts preferentially with the free isocyanate groups remaining in the initial polyurethane reaction product much more readily than does the hydrogen of the water, and therefore the chain is extended by reaction with the piperazine compound even though the reaction takes place in an aqueous medium. The amount of piperazine ordinarily employed Will be that equivalent to the unreacted isocyanate groups remaining in the initial polyurethane reaction product, any excess being removed by washing with water. (The maximum degree of chain extension is theoretically obtained when there are present stoichiometric proportions of the diisocyanate-terminated polymer and the chain-extending agent.) It will be obvious, however, that somewhat lesser amounts may be employed, for the chain extension of the isocyanate-terminated polyurethane can be allowed to be completed with the water in which the piperazine is dissolved. In emulsion polymerization, excess diamine may be used without much affecting molecular weight, since the diamine enters the dispersion of prepolymer gradually, reacting to give maximum chain length; then the excess is washed out. However, as shown by Example 5, the products of emulsion chain extension and solvent chain extension are chemically identical as determined by their infrared absorption spectra.

The amount of water to be employed in the formation of the emulsion is not critical, although in general the minimum amount will be equal in volume to the initial 1Q polyurethane reaction product or the solvent solution or slurry of this product. When too small an amount of Water is employed, emulsions are obtained which are too thick to handle readily while, on the other hand, dispersions which are too dilute are uneconomical to handle due to their excessive volume.

Any emulsifying agent which will give oil-in-water emulsions is satisfactory for use in the present invention. Satisfactory types of emulsifying agents are the polyethylene glycol ethers of long chain alcohols, quaternary ammonium salts, the tertiary amine or alkylol amine salts of long chain alkyl acid sulphate esters, alkyl sulphonic acids or alkyl aryl sulphonic acids and salts thereof; and alkali metal salts of high molecular weight organic acids. Nonionic agents such as polyoxyethylenepolyoxypropylene glycols, are preferred. The pH can then be regulated to a neutral value, preferably not above 7, to minimize any tendency toward hydrolysis. Salts of the high molecular weight organic acids may be used as emulsifying agents. One method of incorporating such salts is to mix the acid, e.g., tall oil, with the prepolymer mass and to have the requisite amount of alkali present in the aqueous bath, so as to form the emulsifier in situ. Although there is presumably some reaction between the acid and the free isocyanate groups in the prepolymer, this is not significant if the mixture is fairly promptly added to the aqueous bath. From 2% to 6% of the emulsifying agent based on the weight of the prepolymer employed will usually be found sutficient to produce stable emulsions. When a fatty acid soap is used as the emulsifying agent, the soap must not be destroyed by acidic substances. The pH must therefore be maintained at least as high as that of an aqueous solution of the soap if stable latices are to be produced. For most fatty acid soaps the pH should be at least 9, and for this reason soaps are not preferred. The small amount of carbon dioxide which may be formed by the chain extension of the isocyanate groups with water is acidic and uses up free alkali in the latex, so that an excess of alkali may be necessary to compensate for this.

Preferably .no alkali is added to the reaction, since some usually remains and causes deterioration of the polymer at elevated temperatures.

The chain extension step, while a relatively fast reaction when employing the piperazine chain extenders of the invention, may frequently be assisted by agitation of the emulsion for some time after its initial formation. This is usually accomplished by means of a conventional paddle type agitator at 30-9O r.p.m. or other conventional stirring equipment such as a Cowles dissolver, which aids in contacting the emulsion droplets with the chain extender.

The polymer may be coagulated from its aqueous dispersion or latex by methods normally employed in the coagulation of rubber or synthetic elastomers from their latices. Common methods for effecting this coagulation are by the addition of acid, for example, acetic acid, or inorganic salts such as sodium chloride or calcium chlo ride. Mere acidification is sometimes not sufficient to coagulate the more stable latices. The addition of salt in addition to acid is often desirable. Usually from twenty to thirty parts of sodium chloride per parts of water in the latex will effect coagulation. When the elastomer is to be precipitated from the latex, smaller amounts or none of the dispersing agent may be used, giving an intentionally less stable latex. In these cases the latex creams, that is, a layer of the polymer collects which may be removed as a coagulum from the top or bottom of the water layer. The latex is preferably coagulated by freezing.

The coa-gulated polymer when removed from the water may be dried on a heated rubber mill or other milling equipment.

The following examples are given to illustrate the invention, but are not to be construed as limiting.

1 1 EXAMPLE 1 (a) Prepolymer formation 8181 parts of urethane grade dihydric polyoxyethylenepolyoxypropylenes, having a molecular weight of about 1065, a polyoxyethylene content of about 15% by weight, and a molecular weight of the polyoxypropylene base of about 940, and 2,619 parts of tolylene diisocyanate isomers (80% of the 2,4 isomer and 20% of the 2,6 isomer) were mixed. The NCO/OH mole ratio was 2.0. The mixture was heated at 120 centigrade for three hours. At the end of this time the viscosity was 9,850 centistokes and the free isocyanate content of this prepolymer was 5.32%.

(b) Chain extension Forty parts of toluene was dissolved in 100 parts of this isocyanate-terminated prepolymer and a solution of five parts of a surface active agent, consisting of dihydric polyoxyethylenepolyoxypropylenes having a molecular weight of about 4,120, a polyoxyethylcne content of about 50% by Weight, and a molecular weight of the polyoxypropylene base of about 2,050, in 100 parts of water was stirred into the prepolymer-toluene solution at a 15,000 rpm. stirring rate over a period of one minute. After one minutes time, a solution of 6.3 parts of 2-methylpiperazine in 25 parts of water was stirred into the prepolymer emulsion. After a short time the emulsion coagulated and a solid urethane-urea polymer separated. The polymer was washed, dried, and molded into sheets. Characteristics of this polymer are shown in Table I.

EXAMPLE 2 (a) Prepolymer formation 3278 parts of dihydric polyoxyethylenepolyoxypropylenes, having a molecular weight of about 1,065, a polyoxyethylene content of about 15 by weight, and a molecular weight of the polyoxypropylene base of about 940, were mixed with 722 parts of tolylene diisocyanate mixed isomers (80/20; 2,4/2,6). The NCO/OH mole ratio was 1.35. The mixture was heated at 120 centigrade for two hours. At the end of this time the viscosity was 38,500 centistokes and the free isocyanate content was 2.27%.

(b) Chain extension 200 parts of toluene were dissolved in 500 parts of this isocyanate-terminated prepolymer and the solution was emulsified in a solution of thirty parts of a surface active agent, consisting of dihydric polyoxyethylenepolyoxypropylenes having a molecular weight of about 10,000, a polyoxyethylene content of about 80% by weight, and a molecular weight of the polyoxypro'pylene base of about 2,250, in 500 parts of water using agitation at 15,000 rpm. After one minute a solution of 13.5 parts of 2- methylpiperazine in 75 parts of water was added with stirring to produce a stable emulsion of a polyurethaneurea polymer. The characteristics of this polymer are shown in Table I.

EXAMPLE 3 (a) Prepolymer formation 4800 parts of polyoxy-propylene glycol of molecular weight averaging 400 were mixed with 3200 parts of tolylene diisocyanate mixed isomers (80% 2,4- and 20% 2,6-tolylene diisocyanate). The NCO/OH mole ratio was 1.60. The mixture was heated at 100 to 110 centigrade for three hours. The prepolymer thus formed was too viscous to flow at room temperature. The free isocyanate content was 6.15%

(b) Chain extension Twenty parts of toluene and 35 parts of cyclohexanone were dissolved in 100 parts of this isocyanate-termin-ated prepolymer and the solution was emulsified in a solution of 6.6 parts of a surface active agent, consisting of dihydric polyoxyethylenepolyoxypropylenes having a molecular weight of about 10,000, a polyoxyethylene content of about by weight, and a molecular weight of the polyoxypropylene base of about 2,250, in parts of water. Stirring at 15,000 rpm. was employed in this operation. After one minute a solution of 7.3 parts of Z-methylpiperazine in 25 parts of water was stirred into the emulsion. After a short time, a light-colored solid polyurethane-urea polymer separated. The polymer was washed, dried, and molded into sheets. Characteristics of this polymer are shown in Table I.

EXAMPLE 4 (a) Prepolymer formation 2910 parts of polyoxypropylene glycol of average molecular weight 1000 were mixed with 1090 parts of tolylene diisocyanate mixed isomers (80/20; 2,4/2,6). The NCO/OH mole ratio was 2.0. The mixture was heated at centigrade for one hour and then at 100 centi-grade for two hours. At the end of this time the viscosity of the product was 15,000 centistokes and the free isocyanate content was 6.96%

(11) Chain extension Twenty parts of toluene and 35 parts of cyclohexanone were dissolved in 100 parts of this isocyanate-terminated prepolymer and the solution was emulsified in a solution of three parts of a surface active agent, consisting of dihydric polyoxyethylenepolyoxypropylenes having a molecular weight of about 10,000, a polyoxyethylene content of about 80% by weight, 'and a molecular weight of the polyoxy propylene base of about 2,250, in 100 parts of water using high speed agitation. Immediately thereafter a solution of 8.3 parts of Z-methylpiperazine was stirred in to produce a stable emulsion of a polyurethaneurea polymer. The emulsion was broken or coagulated by freezing and thawing to give the solid polymer, which was then washed, dried, and molded. Some of its properties are recorded in Table 1.

EXAMPLE 5 (a) Prepolymer formation 9315 parts of polyoxypropy-lene glycol of average molecular weight 2000 were mixed with 1485 parts of mixed isomers (80/ 20; 2,4/2,6) of tolylene diisocyanate. The NCO/OH mole ratio was 1.75. The mixture was heated at 120 centigrade for three hours. The viscosity at 25 centigrade was then 10,100 centipoises and the free isocyanate content was 2.6%

(b) Chain extension Polyurethane-urea polymers were made from this isocyanate-terminated prepolymer by both solution and emulsion techniques.

(i) Forty parts of toluene were dissolved in 100 parts of the above isocyanate-terminated prepolymer and to this solution was added with stirring a solution of 3.1 parts of 2-methylpiper-azine in 27 parts of toluene. The mixture gelled immediately. The polymer was dried and then molded into sheets.

(ii) Fourteen parts of toluene were dissolved in 35 parts of the above isocyanate-terminated prepolymer. This solution was emulsified in a solution of 1.75 parts of a surface active agent, consisting of dihydric polyoxyethylenepolyoxypropylenes having a molecular weight of about 4,120, a polyoxyethy lene content of about 50% by weight, and a molecular weight of the polyoxypropylene base of about 2,050, in 35 parts of water using agitation at 15,000 rpm. After one minute a solution of 1.08 parts of 2-methylpiperazine in 8.75 parts of water was added to this emulsion with stirring. A stable dispersion of polyurethane-urea polymer resulted. This emulsion was coagulated by freezing and then thawing. The polymer was washed, dried, and molded into sheets.

A comparison of the infrared absorption spectra of the materials produced in (i) and (ii) showed the two materials to be chemically identical. The physical characteristics of the polyurethane-urea polymers are shown in Table I.

EXAMPLE 6 (a) Prepolymer formation 3360 parts of dihydric polyoxyethylenepolyoxypropylenes having a molecular weight of about 2,000 and a polyoxyethylene content of about by weight, were mixed with 640 parts of mixed isomers of tolylene diisocyanate (80/20; 2,4/ 2,6). The mixture was heated at 120 centigrade for three hours. At the end of this time the viscosity was 4600 centipoises at 25 centigrade and the free isocyanate content was 4.2%.

(12) Chain extension One hundred parts of this isocyanate-terminated prepolymer were dissolved in 650 parts of ethyl acetate and an additional 13.1 parts of tolylene diisocyanate mixed isomers were added. The NCO/ OH mole ratio was 2.16. 10.8 parts of 2,3,5,6-tetramethylpiperazine was then stirred in. A stable solution of the isocyan-ate-terminated polyurethane-urea polymer was formed. A film of the product was dried, cured eight hours at 120 centigrade, and tested. It had a tensile strength of 3000 psi. and an elongation at break of 500%.

EXAMPLE 7 (a) Prepolymer formation 3360 parts of dihydric polyoxyethylenepolyoxypropylenes having a molecular weight of about 2,000, a polyoxyethylene content of about 15% by weight, and a molecular weight of the polyoxypropylene base of about 1,750, were mixed with 640 parts of mixed isomers (80/20; 2,4/2,6) of tolylene diisocyanate. The NCO/ OH mole ratio was 2.16. The mixture was heated at 120 centigrade for three hours. At the end of this time the viscosity was 4600 centipoises at 25 centigrade and the free isocyanate content was 4.2%.

(b) Chain extension (i) One hundred parts of this isocyanate-terminated prepolymer were dissolved in 100 parts of cyclohexanone and the solution emulsified in 200 parts of water containing four parts of surface active agent, consisting of dihydric polyoxyethylenepolyoxypropylenes having a molecular weight of about 6,760, a polyoxyethylene content of about 70% by Weight, and a molecular weight of the polyoxypropylene base of about 2,050. After one minute a solution of 5.7 parts of cis 2,5-dimethylpiperazine was added with stirring to produce a stable emulsion of the polyurethane-urea polymer. The emulsion was coagulated by freezing and thawing and the polymer was filtered off, washed, dried, and molded. The polymer was soft, light-colored, and could be milled easily on a rubber mill.

(ii) One hundred parts of the above isocyanateterminated prepolymer were dissolved in 100 parts of isopropyl acetate and the solution emulsified in 200 parts of water containing four parts of the surface active agent employed in (i) above. After one minute a solution of 5.7 parts of trans 2,5-dimethylpiperazine was added with stirring to produce a stable emulsion of the polyurethaneurea polymer. The emulsion was coagulated by freezing and thawing and the polymer was filtered off, washed, dried, and molded. The product was a light-colored rubber, harder than that produced using cis 2,5-dimethylpiperazine, and did not mill as easily on a rubber mill. Characteristics of the polymer are shown in Table I.

14 EXAMPLE 8 (a) Prepolymer formation (see Example 7) (b) Chain extension One hundred parts of the prepolymer described in Example 7 and 5.7 parts of 2,6-dimethylpiperazine were separately dissolved in portions of 650 parts of ethyl acetate. The two solutions were mixed and 8.7 parts of mixed isomers of tolylene diisocyanate (/20; 2,4/ 2,6) were added with stirring. A stable solution of the thusproduced polyurethane-urea was formed. The solution was dried and cured sixteen hours at 120 centigrade and the resulting film was tested. Results are shown in Table 1.

EXAMPLE 9.-(COMPARATIVE EXAMPLE) (a) Prepolymer formation 3030 parts of urethane grade dihydric polyoxyethylenepolyoxypropylenes, having a molecular weight of about 1,065, a polyoxyethylene content of about 15% by weight, and a molecular weight of the polyoxypropylene base of about 940, and 970 parts of tolylene diisocyanate isomers (80/20; 2,4/ 2,6) were mixed. The NCO/OH mole ratio was 2.0. The mixture was heated at 120 centigrade for two and one-half hours. At the end of this time the viscosity was 9000 centipoises at 25 centigrade and the free isocyanate content was 5.38%.

(11) Chain extension 5.78 parts of 1,4-butanediol were mixed with parts of this isocyana-te-terminated prepolymer. The mixture was poured into a tray and heated at 70 centigrade for 24 hours. A soft millable polyurethane rubber was obtained. Some characteristics of this material are shown in Table I.

EXAMPLE 10 (a) Prepolymer formation 7475 parts of urethane grade dihydric polyoxyethylenepolyoxypropylenes, having a molecular weight of about 1,065, a polyoxyethylene content of about 15% by weight, and a molecular weight of the polyoxypropylene base of about 940, and 2393 parts of tolylene diisocyanate isomers (80/20; 2,4/2,6) were mixed. The NCO/OH mole ratio was 2.0. The mixture was then heated at centigrade for three hours. At the end of this time the free isocyanate content was 5.37%.

(1)) Chain extension 100 parts of this isocyanate-terminated prepolymer was dissolved in forty parts of toluene and the solution emulsified in a solution of six parts of surface active agent, consisting of dihydric polyoxyethylenepolyoxypropylenes, having a molecular weight of about 10,000, a polyoxyethylene content of about 80% by weight, and a molecular weight of the polyoxypropylene base of about 2,250, in 100 parts of water. After one minute, a solution of 5.5 parts of piperazine in 25 parts of water was added to the emulsion with stirring. A stable suspension of polyurethane-urea polymer resulted. The characteristics of this material are shown in Table I.

EXAMPLE 11.POLYESTER POLYURETHANE PREPOLYMER (a) Prepolymer formation A polyester was made following the formulation and procedure given by N. Seeger in US. Patent 2,760,953 assigned to Goodyear Tire and Rubber Company.

Parts Adipic acid 2630 Ethylene glycol 769 Propylene glycol 650 The mixture was heated to 200 centigrade. Then the pressure was reduced gradually to twenty millimeters of (b) Chain extension 100 parts of this isocyanate-terminated polyurethane prepolymer was dissolved in sixty parts of toluene and the solution was emulsified in a solution of six parts of surface active agent, consisting of dihydric polyoxyethylenepolyoxypropylenes having a molecular weight of about 10,000, a polyoxyethylene content of about 80% by weight, and a molecular weight of the polyoxypropylene base of about 2,250, in 100 parts of water. After one minute a solution of 1.8 parts of Z-methylpiperazine in 25 parts of water was added to the emulsion with stirring. A stable emulsion resulted which was coagulated by freezing and thawing. The polymer was separated, dried and molded into sheets. The characteristics of this polymer are shown in Table 1.

EXAMPLE 12.COMPARATIVE EXAMPLE (a) Prepolymer formation 4800 parts of polyoxypropylene glycol of average molecular weight 400 was mixed with 3200 parts of mixed isomers (80/20; 2,4/2,6) of tolylene diisocyanate. The NCO/OH ratio was 1.6. The mixture was heated at 100 to 110 centigrade for three hours. At the end of this time the isocyanate content of the polyurethane prepolymer was 6.15%.

(b) Chain extension 100 parts of this isocyanate-terminated prepolymer was mixed with 6.6 parts of 1,4-butanediol and sixty parts of toluene. The mixture was heated eighteen hours at 70 Centigrade. After removing the toluene a soft rubber was obtained, the properties of which are shown in Table 1.

EXAMPLE 13.-COMPARATIVE EXAMPLE (a) Prepolymer formation (see Example 11) (17) Chain extension 100 parts of the polyester type isocyanate-terminated prepolymer described in Example 11 was mixed with sixty parts of toluene and 1.65 parts of 1,4-butanediol. The solution was poured into a tray and heated for eighteen hours at 70 centigrade and then for three hours at 120 centigrade. The dry resulting product was soft and sticky and of a tar-like consistency.

EXAMPLE 14.-COMPARATIVE EXAMPLE (a) Prepolymer formation 9315 parts of polyoxypropylene glycol of average molecular weight 200 were mixed with 1485 parts of mixed isomers (80/20; 2,4/2,6) of tolylene diisocyanate. The NCO/ OH mole ratio was 1.75. The mixture was heated at 120 centigrade for four hours and fifteen minutes. The viscosity at 25 centigrade was then 10,100 centipoises and the free isocyanate content was 2.6%.

(17) Chain extension 100 parts of this isocyanate-terminated liquid polyurethane prepolymer was emulsified in a solution of eight parts of surface active agent, consisting of dihydric polyoxyethylenepolyoxypropylenes having a molecular weight of about 10,000, a polyoxpethylene content of about by weight, and a molecular weight of the polyoxypropylene base of about 2,250, in forty parts of water using agitation at 15,000 r.p.m. to effect emulsification. Within one minute a solution of 3.75 parts of 2,4-tolylene diamine in fifteen parts of water was added to the emulsion. A partially stable emulsion of polyurethane-urea polymer was formed which was coagulated by freezing and thawing. The product was separated, washed, dried, and molded into sheets. Characteristics of this polymer are shown in Table I.

EXAMPLE 15.COMPARATIVE EXAMPLE (a) Prepolymer formation 3030 parts of dihydric polyoxyethylenepolyoxpropylenes having a molecular weight of about 1,065, a polyoxyethylene content of about 15% by weight, and a molecular weight of the polyoxypropylene base of about 940, were mixed with 970 parts of mixed isomers (80120; 2,4/2,6) of tolylene diisocyanate. The NCO/OH mole ratio was 2.0. The mixture was heated at 120 centigrade for three hours. The viscosity at 25 centigrade was then 9,000 centipoises and the free isocyanate content was 5.38%.

(b) Chain extension parts of this isocyanate-terminated liquid polyurethane prepolymer were dissolved in 150 parts of isopropyl acetate. To this solution was added a solution of fifteen parts of surface active agent, consisting of dihydric polyoxythylenepolyoxypropylenes having a molecular weight of about 10,000, a polyoxyethylene content of about 80% by weight, and a molecular weight of the polyoxypropylene base of about 2,250, in 250 parts of water with agitation at 15,000 r.p.m. An inversion of phase occurred and an emulsion formed of prepolymer solution in water. Within one minute, a solution of 7.8 parts of 2,4-tolylene diamine in 42.2 parts of isopropyl acetate were added to the emulsion. A stable emulsion of polyurethane-urea polymer was formed which was coagulated by freezing and thawing. The polymer was separated, washed, dried, and molded into sheets. Characteristics of this polymer are shown in Table I.

EXAMPLE I6.COMPARATIVE EXAMPLE (a) Prepolymer formation 4800 parts of polyoxypropylene glycol of average mb-.

(b) Chain extension 100 parts of this isocyanate-terminated semi-solid polyurethane prepolymer was dissolved in twenty parts of toluene and 35 parts of cyclohexanone. The solution was emulsified in a solution of 6.6 parts of surface active agent, consisting of dihydric polyoxyethylenepolyoxypropylenes having a molecular weight of about 10,000, a polyoxyethylene content of about 80% by weight, and a molecular weight of the polyoxypropylene base of about 2,250, in parts of water using agitation at 15,000 r.p.m. Within one minute, a solution of 8.9 parts of 2,4-tolylene diamine in 25 parts of water were added and a stable emulsion of polyurethane-urea polymer resulted. The emulsion was coagulated by freezing and thawing. The polymer was separated, washed, dried, and molded into sheets. Characteristics of this polymer are shown in Table I.

TABLE I.PROPERTIES OF SOME POLYURETHANE-UREA POLYMERS Example l 2 3(e) 4(d) 5i 5ii 6 7i 7ii 8 Diol L31.... L31...- PPG 2000.. PPG 2000. L61 L61 L61 L61.

NCO/OH Mole Ratio 2. 00.-.- 1.35.--. 1. 75 1.75 Free NCO Content of Prepol- 5. 32.... 2. 27.... 2. a 2.6 i See Examplei ymer, percent.

Extending Agent. 2-MP..- 2-MP..- 2-MP. 2-MP 2-MP 2-MP- 2,3,5,6- Cis 2,5- Trans 2,5- 2,6-DMP.

'lMP. DMP. DMP.

ShoreA Hardness, 5 61 4O 43 38 Soft I millable Tensile Strength, p.s.i.. 3, 780... 680..." 630 830 3, 000..." rubber 2,120".-. 1, 340. Elongation at Break, percent.. 1, 550-.. 2,300... 1,500 2,000 0 It 0 400.

so er Stress at 300% 500 110..... 150 130 than 2,100..." 975.

Elongation, p.s 7n) Yield Point, p.s.i

Example 9(a) (b) 10 11 12(a) (c) 13(a) (i) 14(g) 15(11) 16(i) Diol PE PPG 400.... NCO/OH Mole Ratio 1. 50. 1.60..- Free N 00 Content of Prepolymer, percent-. 1. 54 6.15 1. 54 Extending Agent 2-MP-.. lgil-btlitanel-%l)111tfine Shore A Hardness, 5 Tensile Strength, p.s.i Elongation At Break, percent. Stress at 300% Elongztion, p.s.i. Yield Point, p.s.i

(a) =straight polyurethane polymer. (b) =con1parison with Example 1.

(c) =comparison with Example 3.

(d) =excellent properties for an uuvulcanized rubber. (e) =plastic-n0te yield point.

Pip =Piperazine.

2-MP zMethylpip erazine.

cis 2,5-DMP ois 2,5-D imethylpiperazine. trans 2,5 D Ml. trans 2,5-Dimethylpiperazine. 2,6-D MP =2,6-Dirnethylpiperazine. 2,3,5,6-TMP 2,3,5,6-Tetramethylpiperazinc. TDA 2,4-Tolylene diamine.

EXAMPLE 17.COMPARATIVE EXAMPLE- POLYOXYALKYLENE GLYCOL (a) Prepolymer formation 2750 parts of polyoxypropylene glycol of average molecular weight 765 were mixed with 1250 parts of mixed isomers of tolylene diisocyanate (80/20; 2,4/ 2,6) and the mixture was heated at 100 Centigrade for three hours. The NCO/ OH ratio was 2.0/1. At the end of this time, the viscosity at centi-grade was 37,000 centipoises and the isocyanate content was 7.12%.

(12) Chain extension 100 parts of this isocyanate-terminated urethane prepolymer were dissolved in twenty parts of toluene and thirty-five parts of cyclohexanone. The solution was emulsified in .a solution of six parts of surface active agent, consisting of dihydric polyoxyethylenepolyoxypropylenes having a molecular weight of about 10,000, a polyoxyethylene content of about 80% by weight, and a molecular weight of the polyoxypropylene base of about 2,250, in 110 parts of water using agitation at 15,000 rpm. To the emulsion there was added within one minutes time a solution of 10.4 parts of 2,4-tolylenediamine in 25 parts of water. A urethane-urea polymer Was formed which was washed, dried and molded into sheets. Some proper- (i) =comparison with Example 11. (g) =comparisou with Example 5ii. (h)=comparison with Examples 1 and 9. (i) =comparison with Examples 3 and 12.

ties of this polyurethane-urea polymer are shown in 0 Table II.

EXAMPLE 18.POLYOXYALKYLENE GLYCOL (a) Prepolym er formation See Example 17 for prepolymer formation.

(b) Chain extension 100 parts of the isocyanate-terminated urethane prepolymer prepared as in Example 17 were dissolved in forty parts of toluene. To this solution there was added with agitation at 15,000 r.p.rn. a solution of six parts of surface active agent, consisting of dihydric polyoxyethylenepolyoxypropylenes having a molecular weight of about 10,000, a polyoxyethy'lene content of about by Weight, and a molecular weight of the polyoxypropylene base of about 2,250, in parts of water. An inversion of phase occurred and an emulsion of prepolymer solution in water was formed. To the emulsion, within one minute after its preparation, a solution of 8.5 parts of 2- methylpiperazines in 25 parts of water was added. An emulsion of urethane-urea polymer was formed which was coagulated by freezing and thawing. The polymer was separated, washed, dried, and molded into sheets. Some properties of this polyurethane-urea polymer are shown in Table II.

TABLE II.COMPARISON OF URETHANE-UREA POLYMERS PREPARED FROM 'IDA AND Z-MP Glycol L61 L31 L31 2000+ 765* 765 400' NCO/OH Ratio 2.00 2. 1.35 1. 75 2.00 1. 75 1. 60

Extending Agent:

TDA:

Shore A Hardness, 65 77 46 56 91 86 99 Tensile Strength, p.s.i. 850 2, 280 460 470 3, 670 4, 290 5, 000 Elongation at Break, p 1,160 1,160 1, 380 1, 090 370 735 85 Stress at 300% Elong., p.s.i 505 1 000 23 360 3, 100 1,930 2 Mgield Point, p.s.i- 7, 730 Shore A Hardness, 5". 44 61 40 as as 75 9s Tensile Strength, p.s.i 700 3, 780 680 830 6, 590 6, 950 7, 080 Elongation at Break, p 2, 500 1, 550 2, 300 2, 000 620 815 240 Stress at 300% Elong p s i 120 500 11 130 2, 850 1, 220 Yield Point, p.s.i- 4, 950

The above data are on raw, unfilled, unvulcanized stocks pulled at a jaw speed of twenty inches per minute except for the polymers prepared from PPG 400 which were pulled at a aw speed of one inch per minute.

M.W. 1 M W. 2,0

,065, polyoxyethyleue content 15%.

Examples 17 and 18 and Table II, which in itself presents five additional examples therein identified (which for procedure followed the details of Examples 17 and 18), clearly show for the piperazine-extended polyurethanes of the present invention either better processability at tensile strength values equal to those of the tolylene diamine-extended polyurethanes or that, at equal hardness values, the piperazine-extended polyurethanes have greater tensile strength. Likewise, the comparisons of Table I TABLE III.-HARDNESS AND TENSILE STRENGTH VALUES FOR POLY- URETHANES EXTENDED WITH OTHER DIAMINES Prepolymer Composition Extending Shore A Tensile and N CO/OH Ratio Agent Hard ness Strength,

L81-TDI; 2.00/1 TDA- 320 L31-TDI; 1.35/1 TDA 46 460 PPG 2000-TDI; .62/1--- TDA..- 380 PPG 2000-TDI; 1.75/1--- m-Phenylene 51 670 diamine. PPG 2000-TDI; 1.75/1-.- TDA 56 470 Lfil-TDI; 2.00/1 HMDA--- 62 1,020 PPG 2000-1DI; 1.75/1--- m-Xylylene 64 1, 340

diamine. Lfil-TDI; 2.00/1 T 65 850 9 Lfil-TDI; 2.00/1 66 1, 130 1 PPG 2000-TDI 2 00/1--. 72 1, 230 11 L61-DADI; 2.00/1 75 2, 230 12...--. 15 L31-TDI;2.00/1 77 2, 280 13- Table II (6) PPG 765-TDI; 1.75/1 86 4, 200 14 17 PPG 765-TDI; ZOO/1.--- 91 3,670 15 16 PPG 400-TDI;1.60/1 99 5,000

TDI is Tolylene diisocyanate.

DADI is dianisidine diisocyanate.

HMDA is hexamethylencdiamine.

DPM DA is diphenylmethanediaruine.

Other abbreviations are as shown in the preceding tables.

TABLE IIIA.-HARDNESS AND TENSILE STRENGTH VALUES FOR REP- RESENTATIVE PIPERAZINE-EXTENDED POLYURETHANES Abbreviationsjare as shown in the preceding tables.

Curing and compounding Although, as noted previously, many of the piperazine modified polyurethane-ureas of the present invention are characterized by sufiiciently high tensile strength so as not to require vulcanization or cross-linking, where such is desired, they may be cured, for example, by milling into the polymer an organic polyisocyanate such as mentioned previously, or e.g., 2,4-tolylene diisocyanate dimer or N,N'-bis(3-isocyanato-4-methylphenyl)urea, in a ratio of from two to eight parts per 100 parts of polymer While it is being worked on a rubber mill at temperatures of less than 100 centigrade, and then curing the mixture by molding and heating to from 100 to 150 centigrade for from fifteen to sixty minutes. Other curing agents which may be used are tetrachloroquinone, parafiormaldehyde, organic peroxides, and the like. Still other methods of eflecting a cure are available and will be apparent to one skilled in the art.

The elastomers prepared according to the present invention may be used for thesame purposes as other elastomers. They may be molded and shaped and from them may be prepared such articles as tires, inner tubes, belts, hose and tubes, wire and cable jackets, footwear, sponge, coated fabric and various other molded or dipped articles. They may be processed to give thermoplastic or thermosetting coatings, molded articles, or films.

The basic elastomeric properties of these products may be varied, if desired, by suitable compounding. The type and amount of the compounding agent to be used is dependent upon the use for which the elastomer is intended. Some of the more important compounding agents which are of value with these elastomers, especially those based on polyether glycols, are carbon black, clay, silica, talc, zinc and magnesium oxides, titanium dioxide and tetraalkoxides, and plasticizers. Inorganic and organic coloring agents may be incorporated to give Well defined colored products. The natural color of the elastomers is off-white to a pale yellow.

The compounding agent-s may be mixed or incorporated 4 with the product at the same time that polyisocyanate vulcanizing agents are added, if desired. Conventional rubber processing machinery may be used. The resulting compounded stocks may be shaped or cured in conventional rubber industry equipment. Alternatively the stocks may be dissolved or extended with solvents for application to surfaces upon which they may be cured after evaporation of the solvent.

It is to be understood that the invention is not to be limited to the exact details of operation or exact compounds shown and described, as obvious modifications and equivalents will be apparent to one skilled in the art, and the invention is therefore to be limited only by the scope of the appended claim.

Iclaim:

, A process for the preparation of polyurethane-urea polymers containing urea-linked C-lower alkylpiperazine radicals which comprises:

(a) reacting a polyester glycol of the formula:

wherein Z and Z' are hydrocarbon radicals and n is an integer such that the molecular weight of said glycol is at least 750, with a stoichiometric excess of an organic polyisocyanate whereby an isocyanateterminated polyurethane polymer is obtained;

(b) emulsifying said polyurethane polymer in water in the presence of an emulsifying agent, and

(c) chain extending said emulsified polyurethane polymer with from about 0.5 to 1.5 equivalents for each equivalent of said polyurethane polymer of a C-lower alkylpiperazine.

References Cited by the Examiner UNITED STATES PATENTS 2,929,803 3/1960 Frazer 26077.5 2,975,157 3/1961 Katz 26077.5 2,988,538 6/1961 Thomas 260-775 0 LEON J. BERCOVITZ, Primary Examiner.

M. C. JACOBS, Assistant Examiner. 

